//
// Created by wze-zero on 2024/8/24 024.
//
#include <iostream>
#include <iomanip>

using namespace std;

int main() {
    int num1, num2;
    double r;
    cin >> num1 >> num2;
    r = (double) (num1 * num2) / (num1 + num2);
    cout << fixed << setprecision(1) << r << endl;
    return 0;
}